Process for renovating pipes

ABSTRACT

A process for renovating pipes wherein a particulate abrasive material is passed through the pipe to loosen the internal deposits, and after the abrasive material and internal deposits are removed from the pipe, a coating of a curable resinous or plastic material is applied to the interior of the pipe. An alternately produced pressure drop between the two ends of the pipe is employed to cause the particulate abrasive material to reciprocate within the interior of the pipe and thereby effectively loosen the internal deposits and avoid cloggages resulting from the loosened and detached internal deposits.

BACKGROUND OF THE INVENTION

The invention relates to a process for renovating pipes, which comprisesthe steps of removing internal deposits in the pipe by flowing abrasivesand applying an inside coating of a viscous curing material.

Basically, it should be remarked at this point that the pipes to berenovated are already installed lines, which may carry gas, vapor, orliquid. Thus, the pipes may include, for example, feed and/or drainpipes for water or gas in residential, industrial, and municipal areas.This also includes residential and industrial sewer lines. All of theselines tend to form incrustations, which result primarily from calcareousdeposits from the water, corrosion on the inside wall of the pipe,precipitates from the flow medium, products of reaction between the flowmedium and entrained substances as well as the material of the pipe,etc., and from a combination of effects resulting therefrom. Theforegoing phenomena lead to leaks or very considerable reductions of theinside cross sections of the pipes, whereby the transportation of theflow medium is disturbed, if not even prevented.

The presently claimed process for renovating pipes assists in avoiding atotal replacement of the pipes, which turns out to be especiallyadvantageous with respect to completely installed plumbing equipment. Inthis instance, the pipes are more or less freely accessible afterremoval of the fixtures, so as to permit application of the claimedcleaning and coating process. Essential is at any rate that a pipe beaccessible at least at two open ends, so as to be able to carry out theindividual steps of the process. The claimed process does not precludean at least partial conventional repair of the pipes, so that it is alsoquite possible to replace complete pipe systems in part and to renovatesame in part by the claimed process.

Processes of the aforesaid kind have been known from practice for quitesome time. only as an example, reference is made in this context to EP 0299 134. This European Patent discloses a process of this kind, in whichthe removal of internal deposits in the pipes and internal coating ofthe pipes occurs exclusively by means of compressed air. In other words,in the known process, compressed air is forced as a carrier mediumthrough the pipe. When removing internal deposits, the transportation ofthe abrasive, which occurs exclusively by compressed air, leads tocloggages of the pipe, especially in the case of substantial internaldeposits and, thus, requires quite considerable efforts to remove thecloggages. Flat parts that have been torn off by the compressed air areprone to accumulate just in the region of elbows or bends. Eventually,these accumulations will lead to a total blockage of the pipe.

Furthermore, the known method has the great disadvantage that whilecarrying out the process or during the application of compressed air, itis practically impossible to detect leaks. Consequently, there existsthe risk that despite enormous leaks the inside wall is coated, whichpractically prevents a stopping of the leaks. In this respect, a largeleak or hole in the pipe is virtually "improved" by the coating, and canno longer be effectively closed.

It is now the object of the present invention to describe a process forrenovating pipes, which allows to obtain with simple technical means aconveying quality that is comparable with new piping, while avoidingcloggages by internal deposits which become detached during thetreatment.

SUMMARY AND DETAILED DESCRIPTION OF THE INVENTION

The above and other objects and advantages of the present invention areachieved by the provision of a process for renovating pipes comprisingthe steps of introducing an abrasive material into the pipe by means ofa pressure drop between the two ends of the pipe, then alternatelyproducing a pressure drop between the two ends of the pipe so as tocause the abrasive material to reciprocate within the interior of thepipe, and then causing the abrasive material and any loosened internaldeposits to exit from the pipe by means of a pressure drop between thetwo ends of the pipe. Finally, a coating may be applied to the interiorof the pipe, which is subsequently cured.

In accordance with the invention, as soon as an adequate quantity of theabrasive is in the pipe, the abrasive effect is promoted in that theabrasive is caused to reciprocate in the pipe as a result of analternating pressure drop. This feature of the present invention ensuresthat no cloggages develop inside the pipe as a result of detachinginternal deposits. In particular, in the region of pipe elbows or bends,the pipes are effectively prevented from clogging. The advance of theabrasive as a result of an alternating pressure drop, i.e. thealternating motion of the abrasive inside the pipe continues until thepipe is totally freed from internal deposits, however at least until theabrasive is able to flow unhindered through the pipe. Once such asituation is reached, the further "cleaning process" can be accomplishedeven without an alternating pressure drop, simply by a predeterminedpressure drop and the therefrom resulting advance of the abrasivethrough the pipe. In other words, the abrasive is finally caused to exitfrom the pipe as a result of a pressure drop between the two ends of thepipe. This may be a continuous operation, in which additional abrasiveis sucked in by the pipe or blown thereinto at the inlet end.

Within the scope of a particularly advantageous generation of thepressure drop it will be of advantage, when the abrasive is caused toenter into the pipe from one end by a vacuum.

In this connection, it has been recognized that on the one hand thecompressed air used in the state of the art may lead to damage of thepipe being renovated, or that is causes cloggages in the pipe. On theother hand, it will bring along considerable environmental stress,unless specific measures are taken, since the compressed air that isblown into the pipe under overpressure may exit, at the outletend--under very high pressures--into the environment together withharmful substances. Accordingly, special collection and filter devicesare required irrespective of, or aside from the compressed-airgeneration at the inlet end, which requires additional apparatus and,thus, involves also considerable costs. Other than for the vacuumgeneration, additional equipment is no longer needed as a result of theadvantageous layout, inasmuch as suction occurs only at one end of thepipe, and the sucked-in air is collected or received, together withparticles or the like, in an apparatus preceding the suction device.Added to this is the special advantage that, with a suction occurring onone side, the process can be carried out from one side of the pipe,namely from the suction side. It is only necessary to enter the viscouscoating material at the free end, which may occur prior to the suction,so that again a single operator can start and carry out the actualcoating operation at the suction end.

Furthermore, the advantageous layout of the process in accordance withthe invention brings along the considerable advantage that the vacuumgenerated at the suction end drops toward the open end of the pipe.Consequently, as the distance from the outlet end or vacuum enddecreases, detached particles are pulled along to a greater extent, sothat as a result of the drop occurring in direction toward the outletend, cloggages are effectively prevented, inasmuch as same are detachedand entrained respectively to a greater extent with a decreasingdistance from the outlet end. Finally, the process of the presentinvention facilitates detection of leaks, in that in the presence of aleak a lesser vacuum adjusts at the outlet end. When this drop of thevacuum occurs suddenly, same indicates a hole that has suddenly beentorn open in the pipe.

Advantageously, the motion of the abrasives inside the pipes isgenerated in that the abrasive is caused to reciprocate in the pipe byalternating vacuum and overpressure. In other words, once it isaccomplished that vacuum alternates with overpressure in the pipe, theabrasive is alternatingly sucked and blown therethrough. Likewisehowever, it is possible to cause the abrasive to reciprocate in the pipeby alternately applying a vacuum to both ends of the pipe. In this case,the above-described advantages are given. Finally, it is also possibleto cause the abrasive to reciprocate in the pipe, in that overpressureis alternatingly applied to both ends of the pipe. In this instance, theoverpressure is effectively used for advancing the abrasive only in theabsence of substantial leaks in the pipe.

As regards a special, environment-protective realization of the process,it will be of advantage, when the preheated air that is used to dry thepipe is not simply sucked off, but rather sucked respectively out of, orthrough the pipe via a filter device. This filter device may directlyprecede the compressor, so that no special tools are needed.

The abrasive serving to remove the internal deposits could be particlesof any kind that are carried by flowing air. However, these particleswould have to be harder than the internal deposits that are to beremoved. In this connection, particles having a grain size in the rangefrom 0.3 mm to 6 mm have shown to be satisfactory, in particular in therenovation of water lines. A specific weight of more than 3.0 g/cm³ haslikewise been found advantageous. In this case, air is used as carriermedium. In the concrete case, the abrasive particles could be corundumor quartz sand. It would likewise be possible to provide the abrasiveparticles in the form of metallic particles, in particular ferromagneticparticles. These particles will permit a subsequent magnetic separationof the abrasive particles from the detached internal deposits, whichconsist, as aforesaid, of rust and/or lime.

The application of the coating material and, thus, on the one hand asatisfactory wetting with the inside wall of the pipe and, on the otherhand, a rapid subsequent curing are favored in particular in that, afterremoval of the internal deposits, the pipe is heated to a temperatureabove room temperature. In this connection, a temperature of about 40°C. has shown to be especially satisfactory. The heating of the pipecould again occur by sucking therethrough heated air, which is suckedthrough the pipe until the desired temperature is reached at the outletend. This temperature could again be determined via the temperature dropbetween the inlet end and the outlet end of the pipe. Anyhow, it ispreferable that the heating of the pipe occur by sucking therethroughheated air and not by forcing therethrough compressed air. Finally, thepreheated air serving to heat the pipe could also be sucked off via afilter device, which may likewise precede directly the compressor thatis used for the suction.

Furthermore, in a very advantageous manner, the heating of the pipecould occur exclusively or additionally by means of a heating devicewhich is sucked into the pipe after the cleaning and before applying theinside coating. In this respect, it would not be absolutely necessarythat the heated air be sucked in, should the heating device that issucked into the pipe have an adequate capacity. Just in the case ofextremely long pipes, the heating device would at least be capable ofpreventing a cooling of the air that is sucked in at one end, so thatthe heating process is quite considerably accelerated. In a furtheradvantageous manner, the heating device used to this end could be aheating wire, in particular a self-regulating heating wire. Such aheating wire could be constructed in the fashion of a resistance heaterwith a ceramic insulation of the heating conductor. However, inprinciple it is possible to use all devices that can be inserted orsucked into a pipe.

As regards an effective heating of the pipe, it will be of furtheradvantage, when the heating wire extends through the pipe substantiallyover the entire length thereof. An even heating of the pipe is thusguaranteed.

With respect to inserting the heating wire, it will be especiallyadvantageous, when same is sucked into the pipe by means of a towsystem. The tow system could include a kind of parachute or the like,which is engaged by the air flow that develops as a result of thevacuum, and which pulls along the heating wire.

After the pipe is adequately heated, the heating wire is again pulledout of the pipe, advantageously before applying the inside coating. Inso doing, the heating wire could be pulled out both from the inlet endand from the outlet end, i.e., from the vacuum side. In the latter case,it would be necessary to disconnect the power terminals at the inletend.

Thereafter, the coating material is fed into the heated pipe. Also inthis instance, a vacuum is generated at the outlet end. As a result ofthis vacuum, the coating material is sucked together with the ambientair into the pipe. In this process, the different viscosity between theair and the coating material causes the viscose coating material to comeinto contact with the pipe and to wet same. With the use of resin,synthetic resin, or plastic as coating material, the inside wall of thepipe receives a seamless coating. The pressure difference necessary topull in the coating material is generated exclusively by the vacuum atthe outlet end.

In the case of substantial leaks, the coating material may containembedded fibers, in particular short-staple fibers, which may veryadvantageously be glass fibers. Due to the irregularly shaped openings,the glass fibers will come to lie crosswise or interlace thereat, andprovide the viscous coating material with an adequate hold for stoppingthe leak. In this respect, it would be possible to close at least smallholes and stop leaks.

Furthermore, in particular for preventing further environmental stressor necessary waste disposal, it would be very advantageous to measurethe quantity of the coating material supplied to the free end of thepipe such that the inside wall of the pipe as a whole is entirelycoated, however without substantial quantities of the coating materialexiting from the pipe at the suction end. In other words, based on thenormally resulting coating thickness and the length of the pipe beingcoated, it would be possible to predetermine the required quantity ofcoating material at least approximately, without having quantities ofcoating material exit at the suction end and without having to disposeof same.

Furthermore, the process of the present invention permits a temporaryclosing of the free end of the pipe, while suction occurs at one end. Inthis instance, the gradually developing vacuum will facilitate detectionof possible leaks. When hardly any vacuum is obtained, the pipe systembeing renovated has a substantial leak.

Should it be desired to check, for example, the already cleaned pipe forits condition before the actual coating operation, or should it bedesired to examine the quality of the coating after same is applied, itwould likewise be possible to suck, to this end, into the pipe anoptical means for inspecting the pipe or for a quality control of theinside coating. Likewise in this instance, it would be possible to use atow system as an auxiliary means. In the simplest case, the opticalmeans could be a fiber glass line capable of bringing light into thepipe on the one hand, and of bringing out from the pipe light beams thathave been reflected therein. It is possible to provide for this purposefiber bundles or different fiber lines with different functions. A veryparticular embodiment of optical means could comprise a kind ofendoscope, i.e., a miniature camera that can be sucked into the pipewith a corresponding illumination, and even with a miniaturized,remote-control tool for taking samples, or the like.

Finally, it should be emphasized that the claimed process may comprisenumerous, further advantageous process steps, without departing from thespirit of the invention as set forth in the appended claims.

I claim:
 1. A process for renovating pipes comprising the stepsofintroducing an abrasive material into the interior of pipe by means ofa pressure drop between two ends of the pipe, alternately producing apressure drop between the two ends of the pipe so as to cause theintroduced abrasive material to reciprocate within the interior of thepipe, causing the abrasive material and any loosened internal depositsto exit from the pipe by means of a pressure drop between the two endsof the pipe, and then applying a coating to the interior of the pipe. 2.The process as defined in claim 1 wherein the step of introducing anabrasive material into the interior of the pipe includes causing theabrasive material to enter into one end of the pipe by means of avacuum.
 3. The process as defined in claim 1 wherein the step ofalternately producing a pressure drop between the two ends of the pipeincludes alternately applying a vacuum and an overpressure to theinterior of the pipe.
 4. The process as defined in claim 1 wherein thestep of alternately producing a pressure drop between the two ends ofthe pipe includes alternately applying a vacuum to both of the ends ofthe pipe.
 5. The process as defined in claim 1 wherein the step ofalternately producing a pressure drop between the two ends of the pipeincludes alternately applying an overpressure to both of the ends of thepipe.
 6. The process as defined in claim 1 wherein the step of applyinga coating to the interior of the pipe includes sucking a coatingmaterial into one end and through the pipe.
 7. The process as defined inclaim 1 comprising the further step of drying the interior of the pipeprior to the step of causing the abrasive material to reciprocate withinthe interior of the pipe.
 8. The process as defined in claim 7 whereinthe step of drying the interior of the pipe includes causing heated airto flow through the pipe by applying a vacuum to one end of the pipe. 9.The process as defined in claim 8 wherein the step of causing heated airto flow through the pipe includes passing the heated air through afilter after the heated air passes through the pipe.
 10. The process asdefined in claim 1 wherein the abrasive material is particulate.
 11. Theprocess as defined in claim 10 wherein the particulate abrasive materialhas a grain size which averages in the range from 0.3 mm to 6 mm. 12.The process as defined in claim 11 wherein the particulate abrasivematerial has a specific weight greater than 3.0 g/cm³.
 13. The processas defined in claim 10 wherein the particulate abrasive materialcomprises corundum or quartz sand.
 14. The process as defined in claim10 wherein the particulate abrasive material comprises ferromagneticparticles.
 15. The process as defined in claim 1 comprising the furtherstep of heating the pipe to a temperature above ambient temperatureafter the step of causing the abrasive material and any loosenedinternal deposits to exit from the pipe.
 16. The process as defined inclaim 15 wherein the step of heating the pipe includes passing heatedair therethrough and so as to heat the pipe to about 40° C.
 17. Theprocess as defined in claim 16 wherein the step of passing heated airthrough the pipe includes passing the heated air through a filter afterthe heated air passes through the pipe.
 18. The process as defined inclaim 15 wherein the step of heating the pipe includes passing a heatingdevice through the pipe.
 19. The process as defined in claim 18 whereinthe step of passing a heating device through the pipe includes passing aheating wire through the pipe by means of a towing device.
 20. Theprocess as defined in claim 1 wherein the step of applying a coating tothe interior of the pipe includes passing a coating material through thepipe with air.
 21. The process as defined in claim 1 wherein the step ofapplying a coating to the interior of the pipe includes preheating theinterior of the pipe, passing a viscous curable coating material throughthe interior of the pipe with air to wet the same and form anessentially seamless coating, and then causing the coating material tocure.
 22. The process as defined in claim 21 wherein the coatingmaterial comprises a curable resin or plastic.
 23. The process asdefined in claim 21 wherein the coating material includes fibers. 24.The process as defined in claim 21 wherein the step of passing a viscouscurable coating material through the pipe includes introducing ameasured quantity of coating material into a free end of the pipe, whileapplying a suction to an opposite end of the pipe, and with the measuredquantity being predetermined so as to coat the entirety of the insidewall of the pipe without having significant amounts of the coatingmaterial exiting from the opposite suction end of the pipe.
 25. Theprocess as defined in claim 21 comprising the further subsequent step ofinspecting the coating of the coating material on the interior of thepipe and including passing an optical device through the pipe.
 26. Theprocess as defined in claim 25 wherein t he optical device comprises afiber glass line.
 27. The process as defined in claim 25 wherein theoptical device comprises an endoscope.
 28. The process as defined inclaim 1 comprising the further step of detecting for leaks in the pipeby drawing a vacuum at one end of the pipe while closing the oppositeend and monitoring the vacuum level in the pipe.